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白洋淀沉积物氮时空变化特征及其影响因素

Spatial and temporal dynamics of sediment-associated nitrogen and their influencing factors in Baiyangdian Lake

  • 摘要: 氮是引起湖泊水体富营养化的重要因子,湖泊沉积物氮动态变化显著影响着湖泊水环境安全和水生态系统健康。为了解白洋淀沉积物氮的时空动态特征及其影响因素,研究了全淀范围内沉积物不同形态氮含量的空间分布特征以及典型挺水植物和沉水植物分布区各形态氮含量的季节变化特征,识别了沉积物氮含量的关键影响因素。研究结果表明,在白洋淀全淀尺度上,沉积物全氮(TN)质量分数平均值为3.17 mg/g,且以有机氮为主要赋存形态;除硝态氮(\mathrmNO_3^- -N)外,白洋淀沉积物氮含量存在高空间变异性。挺水植物分布区沉积物TN含量的最高值出现在夏季,而沉水植物分布区沉积物TN含量的季节性差异不显著(p>0.05);不同植物分布区沉积物铵态氮(\mathrmNH_4^+ -N)和\mathrmNO_3^- -N平均含量的最高值均出现在秋季,但在相同季节两个植物分布区之间不存在显著差异(p>0.05)。生态网络分析结果表明,在全淀尺度上,全碳、有机质、溶解态有机碳、粉粒含量和C/N比是白洋淀沉积物不同形态氮含量的关键影响因素,而在典型淀区不同植物分布区则以沉积物pH、C/N比、全碳和有机质为关键影响因素。

     

    Abstract: Nitrogen is an important factor influencing eutrophication in lakes, and the dynamics of sediment-associated nitrogen contents can significantly affect water security and aquatic ecosystem health. The Baiyangdian Lake is the largest shallow macrophyte-dominated lake in the North China Plain, playing important roles in supplying water, storing floods and regulating regional climate. The ecological and environmental status of this lake has been given more concerns since Baiyngdian Lake serves as the important ecological barrier of Xiong’an New Area. However, Baiyangdian Lake was facing the eutrophication under the effects of anthropogenic activities and global climate change, and thus some water environment control and ecological water supplying projects have been implemented to protect water quality. Nevertheless, little information is available on nitrogen dynamics in sediments of this lake after these projects. To investigate the spatiotemporal dynamics of nitrogen in sediments and their influencing factors in Baiyangdian Lake, spatial distribution patterns of various forms of nitrogen throughout the entire lake and seasonal variation characteristics in typical vegetation zones (i.e., emergent and submerged plant communities) in typical sub-lakes were investigated and the key factors were identified. The results showed that, on the whole-lake scale, the mean total nitrogen content in sediments reached 3.17 mg/g, with organic nitrogen constituting the dominant nitrogen form. Notably, all nitrogen forms exhibited substantial spatial variabilities except for nitrate nitrogen. On the sub-lake scale, the maximal TN concentration in emergent vegetation areas were observed in summer, whereas submerged vegetation areas showed no significant seasonal variations (p>0.05). Both ammonium nitrogen and nitrate nitrogen concentrations peaked in autumn in both two vegetation areas, though the differences in ammonium nitrogen and nitrate nitrogen between two vegetation areas in the same sampling season remained statistically insignificant (p>0.05). Ecological network analysis results demonstrated the distinct influencing factors for nitrogen forms in Baiyangdian Lake at different space scales. The total carbon, organic matter, dissolved organic carbon, silt contents, and C/N ratios were identified as key factors influencing nitrogen forms on the whole-lake scale, while pH values, C/N ratios, total carbon, and organic matter were the key factors in different vegetation areas on the sub-lake scales. The findings of this work will contribute to better understanding the effects of nitrogen cycling on water quality in the shallow lakes and to improving hydroecological functions and ecological services of these ecosystems.

     

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